Data centers typically host clusters of hundreds and sometimes thousands of servers. Power and energy consumption have thus become key concerns in data centers. <p>Realizing the differences between portable and server-class workloads and operating environments, researchers have developed server-specific management strategies. Despite these efforts, much must still be done. In addition to conserving power and energy in heterogeneous server clusters composed of a combination of traditional and blade servers, the authors and their colleagues also seek to enforce limits on the power each server consumes.</p>